I ended up having to do a Windows Reset by forcing the boot-up sequence to fail by turning the PC off toward the end of boot (since I couldn't enable the Reset using the Windows Settings that failed to load). This wiped all account info (I had previously moved all data files to an external drive), but allowed me to add back each MS account I had on the PC.
I then set Windows Update to allow me to review all updates before installation, so that the Nvidia drivers won't automatically install.